#include "stdafx.h"
#include "MyMD5.h"

/* Define the static member of MD5. */
const byte MyMD5::PADDING[64] = { 0x80 };
const char MyMD5::HEX_NUMBERS[16] = {
	'0', '1', '2', '3',
	'4', '5', '6', '7',
	'8', '9', 'a', 'b',
	'c', 'd', 'e', 'f'
};


/**
* @Construct a MD5 object with a string.
*
* @param {message} the message will be transformed.
*
*/
MyMD5::MyMD5(const string& message) {
	finished = false;
	/* Reset number of bits. */
	count[0] = count[1] = 0;
	/* Initialization constants. */
	state[0] = 0x67452301;
	state[1] = 0xefcdab89;
	state[2] = 0x98badcfe;
	state[3] = 0x10325476;

	/* Initialization the object according to message. */
	init((const byte*)message.c_str(), message.length());
}

/**
* @Generate md5 digest.
*
* @return the message-digest.
*
*/
const byte* MyMD5::getDigest() {
	if (!finished) {
		finished = true;

		byte bits[8];
		bit32 oldState[4];
		bit32 oldCount[2];
		bit32 index, padLen;

		/* Save current state and count. */
		memcpy(oldState, state, 16);
		memcpy(oldCount, count, 8);

		/* Save number of bits */
		encode(count, bits, 8);

		/* Pad out to 56 mod 64. */
		index = (bit32)((count[0] >> 3) & 0x3f);
		padLen = (index < 56) ? (56 - index) : (120 - index);
		init(PADDING, padLen);

		/* Append length (before padding) */
		init(bits, 8);

		/* Store state in digest */
		encode(state, digest, 16);

		/* Restore current state and count. */
		memcpy(state, oldState, 16);
		memcpy(count, oldCount, 8);
	}
	return digest;
}

/**
* @Initialization the md5 object, processing another message block,
* and updating the context.
*
* @param {input} the input message.
*
* @param {len} the number btye of message.
*
*/
void MyMD5::init(const byte* input, size_t len) {

	bit32 i, index, partLen;

	finished = false;

	/* Compute number of bytes mod 64 */
	index = (bit32)((count[0] >> 3) & 0x3f);

	/* update number of bits */
	if ((count[0] += ((bit32)len << 3)) < ((bit32)len << 3)) {
		++count[1];
	}
	count[1] += ((bit32)len >> 29);

	partLen = 64 - index;

	/* transform as many times as possible. */
	if (len >= partLen) {

		memcpy(&buffer[index], input, partLen);
		transform(buffer);

		for (i = partLen; i + 63 < len; i += 64) {
			transform(&input[i]);
		}
		index = 0;

	}
	else {
		i = 0;
	}

	/* Buffer remaining input */
	memcpy(&buffer[index], &input[i], len - i);
}

/**
* @MD5 basic transformation. Transforms state based on block.
*
* @param {block} the message block.
*/
void MyMD5::transform(const byte block[64]) {

	bit32 a = state[0], b = state[1], c = state[2], d = state[3], x[16];

	decode(block, x, 64);

	/* Round 1 */
	FF(a, b, c, d, x[0], s11, 0xd76aa478);
	FF(d, a, b, c, x[1], s12, 0xe8c7b756);
	FF(c, d, a, b, x[2], s13, 0x242070db);
	FF(b, c, d, a, x[3], s14, 0xc1bdceee);
	FF(a, b, c, d, x[4], s11, 0xf57c0faf);
	FF(d, a, b, c, x[5], s12, 0x4787c62a);
	FF(c, d, a, b, x[6], s13, 0xa8304613);
	FF(b, c, d, a, x[7], s14, 0xfd469501);
	FF(a, b, c, d, x[8], s11, 0x698098d8);
	FF(d, a, b, c, x[9], s12, 0x8b44f7af);
	FF(c, d, a, b, x[10], s13, 0xffff5bb1);
	FF(b, c, d, a, x[11], s14, 0x895cd7be);
	FF(a, b, c, d, x[12], s11, 0x6b901122);
	FF(d, a, b, c, x[13], s12, 0xfd987193);
	FF(c, d, a, b, x[14], s13, 0xa679438e);
	FF(b, c, d, a, x[15], s14, 0x49b40821);

	/* Round 2 */
	GG(a, b, c, d, x[1], s21, 0xf61e2562);
	GG(d, a, b, c, x[6], s22, 0xc040b340);
	GG(c, d, a, b, x[11], s23, 0x265e5a51);
	GG(b, c, d, a, x[0], s24, 0xe9b6c7aa);
	GG(a, b, c, d, x[5], s21, 0xd62f105d);
	GG(d, a, b, c, x[10], s22, 0x2441453);
	GG(c, d, a, b, x[15], s23, 0xd8a1e681);
	GG(b, c, d, a, x[4], s24, 0xe7d3fbc8);
	GG(a, b, c, d, x[9], s21, 0x21e1cde6);
	GG(d, a, b, c, x[14], s22, 0xc33707d6);
	GG(c, d, a, b, x[3], s23, 0xf4d50d87);
	GG(b, c, d, a, x[8], s24, 0x455a14ed);
	GG(a, b, c, d, x[13], s21, 0xa9e3e905);
	GG(d, a, b, c, x[2], s22, 0xfcefa3f8);
	GG(c, d, a, b, x[7], s23, 0x676f02d9);
	GG(b, c, d, a, x[12], s24, 0x8d2a4c8a);

	/* Round 3 */
	HH(a, b, c, d, x[5], s31, 0xfffa3942);
	HH(d, a, b, c, x[8], s32, 0x8771f681);
	HH(c, d, a, b, x[11], s33, 0x6d9d6122);
	HH(b, c, d, a, x[14], s34, 0xfde5380c);
	HH(a, b, c, d, x[1], s31, 0xa4beea44);
	HH(d, a, b, c, x[4], s32, 0x4bdecfa9);
	HH(c, d, a, b, x[7], s33, 0xf6bb4b60);
	HH(b, c, d, a, x[10], s34, 0xbebfbc70);
	HH(a, b, c, d, x[13], s31, 0x289b7ec6);
	HH(d, a, b, c, x[0], s32, 0xeaa127fa);
	HH(c, d, a, b, x[3], s33, 0xd4ef3085);
	HH(b, c, d, a, x[6], s34, 0x4881d05);
	HH(a, b, c, d, x[9], s31, 0xd9d4d039);
	HH(d, a, b, c, x[12], s32, 0xe6db99e5);
	HH(c, d, a, b, x[15], s33, 0x1fa27cf8);
	HH(b, c, d, a, x[2], s34, 0xc4ac5665);

	/* Round 4 */
	II(a, b, c, d, x[0], s41, 0xf4292244);
	II(d, a, b, c, x[7], s42, 0x432aff97);
	II(c, d, a, b, x[14], s43, 0xab9423a7);
	II(b, c, d, a, x[5], s44, 0xfc93a039);
	II(a, b, c, d, x[12], s41, 0x655b59c3);
	II(d, a, b, c, x[3], s42, 0x8f0ccc92);
	II(c, d, a, b, x[10], s43, 0xffeff47d);
	II(b, c, d, a, x[1], s44, 0x85845dd1);
	II(a, b, c, d, x[8], s41, 0x6fa87e4f);
	II(d, a, b, c, x[15], s42, 0xfe2ce6e0);
	II(c, d, a, b, x[6], s43, 0xa3014314);
	II(b, c, d, a, x[13], s44, 0x4e0811a1);
	II(a, b, c, d, x[4], s41, 0xf7537e82);
	II(d, a, b, c, x[11], s42, 0xbd3af235);
	II(c, d, a, b, x[2], s43, 0x2ad7d2bb);
	II(b, c, d, a, x[9], s44, 0xeb86d391);

	state[0] += a;
	state[1] += b;
	state[2] += c;
	state[3] += d;
}

/**
* @Encodes input (unsigned long) into output (byte).
*
* @param {input} usigned long.
*
* @param {output} byte.
*
* @param {length} the length of input.
*
*/
void MyMD5::encode(const bit32* input, byte* output, size_t length) {

	for (size_t i = 0, j = 0; j < length; ++i, j += 4) {
		output[j] = (byte)(input[i] & 0xff);
		output[j + 1] = (byte)((input[i] >> 8) & 0xff);
		output[j + 2] = (byte)((input[i] >> 16) & 0xff);
		output[j + 3] = (byte)((input[i] >> 24) & 0xff);
	}
}

/**
* @Decodes input (byte) into output (usigned long).
*
* @param {input} bytes.
*
* @param {output} unsigned long.
*
* @param {length} the length of input.
*
*/
void MyMD5::decode(const byte* input, bit32* output, size_t length) {
	for (size_t i = 0, j = 0; j < length; ++i, j += 4) {
		output[i] = ((bit32)input[j]) | (((bit32)input[j + 1]) << 8) |
			(((bit32)input[j + 2]) << 16) | (((bit32)input[j + 3]) << 24);
	}
}


/**
* @Convert digest to string value.
*
* @return the hex string of digest.
*
*/
string MyMD5::toStr() {
	const byte* digest_ = getDigest();
	string str;
	str.reserve(16 << 1);
	for (size_t i = 0; i < 16; ++i) {
		int t = digest_[i];
		int a = t / 16;
		int b = t % 16;
		str.append(1, HEX_NUMBERS[a]);
		str.append(1, HEX_NUMBERS[b]);
	}
	return str;
}